Reliability based assessment of buildings under earthquakes due to gas extraction
R.D.J.M. Steenbergen, A.C.W.M. Vrouwenvelder
TNO, Structural Reliability, Delft, the Netherlands
In the northern part of the Netherlands over de last decades shallow earthquakes are induced due to large scale gas extraction from the Groningen gas field. Earthquakes occur due to the compaction of the reservoir rock, which leads to subsidence at surface and strain build-up in the reservoir rock and existing faults. The induced earthquakes differ from the better known tectonic earthquakes all over the world, caused by movement of the earth at large depths. The structures affected by the earthquakes however have never been engineered to withstand earthquakes. Layout of the walls and standard constructional details can lead to dangerous partial collapse like fall of walls, opening of cracks and even to total collapse. In the Dutch Building Decree safety criteria for human life have been established and quantified in target level for the Individual Risk. Based on this requirement, in this paper, a reliability based method is developed for the design of new structures and assessment of existing structures for the area affected by the Groningen gas field. This method is adopted in the actual Dutch Guideline NPR 9998 which will be after some years be replaced by the Dutch National Annex to the Eurocode Earthquakes.
Key words: Induced earthquakes, reliability assessment, individual risk, seismic hazard, existing structures, probabilistic design